柠檬酸钠强化剩余污泥酶水解和酸化的研究

厌氧条件下,研究了阳离子络合剂柠檬酸钠(SC)对剩余污泥酶水解和酸化的影响.结果表明:络合剂SC提高了污泥酶水解和酸化的效率,溶解性蛋白质和碳水化合物溶出量增加,SC的最佳投加剂量为0.432 g·g-1(以TS计,下同).络合剂SC可以提高污泥中短链脂肪酸(SCFAs)的积累量,同时减少达到最大SCFAs积累的时间,缩短厌氧消化时间.空白对照组和蛋白酶组的总SCFAs积累量分别在反应第7 d和第6 d达到最大值,而SC+蛋白酶组(SC 0.432 g·g-1)在反应第2 d就达到了最大值.从酶活性的变化和SEM图可知,SC的投加破坏了EPS的网络结构,原来被束缚、隐藏于污泥基体中的水解酶得到释放,从而提高了污泥水解速率.     

外加酶强化剩余污泥水解的研究

采用向污泥中外加酶强化污泥水解的处理方式,考察了单一酶和复合酶的加入对城市污水厂剩余污泥的破解及减量化的影响,并探讨了酶水解过程动力学.结果表明,外加酶可以促进污泥中悬浮固体的溶解和大分子有机物的降解.当酶最佳投加量(以TS中加入酶量计)为60 mg/g时,淀粉酶比蛋白酶的水解效果好,SCOD/TCOD由16.3%上升到22.3%,VSS去除率由39.8%提高到54.24%.同时,复合酶的水解效果较单一酶的效果好,当水解温度为50℃,蛋白酶和淀粉酶的比例为1∶3时,水解效果最佳,VSS去除率达68.43%,还原糖、NH+4-N浓度分别由37.29和47.60 mg/L增加至177.8和143.43 mg/L.酶水解过程的前4 h,蛋白酶和淀粉酶活力均呈上升趋势,符合一级反应动力学,水解4 h左右达最大值,分别为2.57 U/mL和4.64U/mL,之后酶活力逐渐下降.     

混合外源菌强化剩余污泥微氧水解产酸

利用外源投加酵母菌与醋酸菌的方式促进了剩余污泥水解产生短链挥发性脂肪酸（SCFAs）的产量,考察了混合投加模式下污泥水解溶出的正磷酸盐、氨氮和溶解性COD的浓度,研究水解过程胞外聚合物（EPS）组分中蛋白质及多糖的变化特征.结果表明,在酵母菌和醋酸菌投加量分别为10和20g/L时,发酵第5d实现了最高的SCFAs产量,达到719mgCOD/gVSS,其中乙酸含量为328.78mgCOD/gVSS,占总SCFAs的45.72%.投加两种菌显著促进了剩余污泥水解产生SCFAs,且以乙酸为主.外源菌投加促进了水解酸化过程氨氮和正磷酸盐的释放,最佳反应条件下最大释放量分别为80.66和22.38mg/gVSS,有利于从剩余污泥中回收氮磷.投加外源菌后EPS中的蛋白质和多糖从内层向最外层释放,为污泥水解产酸提供底物.外源投加酵母菌与醋酸菌是促进剩余污泥水解酸化的有效手段.     

生物表面活性剂强化污泥水解的研究

为了解生物表面活性剂对剩余污泥水解效果的影响,采用向污泥中投加鼠李糖脂的方式,研究了水解时间、生物表面活性剂投加量以及pH值对污泥水解过程的影响.结果表明,鼠李糖脂显著降低了污泥水解液的表面张力,促进了悬浮固体的溶解和胞外酶的溶出,从而强化了污泥水解.污泥水解过程中,SCOD、蛋白质和还原糖的浓度均呈现先增加后降低的趋势,前6 h内符合一级反应动力学.在鼠李糖脂最佳投加剂量0.3 g.g-1下反应6 h,SCOD、蛋白质和还原糖的浓度分别由371.9、93.3和9.0 mg.L-1上升到3 994.5、800.0和401.7 mg.L-1.生物表面活性剂对污泥水解的强化作用受pH值的影响,随着pH值的增大,水解效率不断增大.当pH=11时,水解效率达到最大值,SCOD、蛋白质和还原糖的浓度分别为5 249.9、1 658.3和597.1 mg.L-1.     

基于微波预处理的酶强化污泥水解酸化研究

微波预处理能显著提高污泥上清液中溶解性有机物含量,进而可作为内碳源补充强化生物脱氮,但释放的大量溶解性有机物却存在碳源可利用性偏低问题.因此,为了提高上述碳源的可利用性,本研究通过批量试验,考察了添加中性蛋白酶和中温α-淀粉酶对微波预处理污泥水解酸化的强化效果,同时研究了水解酸化过程中污泥上清液中有机物的变化特征.结果表明,经过微波-过氧化氢-碱预处理的污泥进行水解酸化能产生较多的挥发性脂肪酸(VFA),碳源可利用性提高,但由于在水解酸化最初的2 d内存在产酸滞后期,导致水解酸化时间被延长.加入中性蛋白酶和中温α-淀粉酶不仅促进了预处理后污泥的水解酸化,而且解除了微波-过氧化氢-碱预处理导致的产酸滞后现象.在55℃、I/S(接种比)=0.07条件下,酶的最佳投加量分别为30 mg·g~(-1)(蛋白酶/总固体浓度TS)和90 mg·g~(-1)(淀粉酶/TS),最佳水解时间为0.5 d,最佳酸化时间为4 d.水解酸化过程中溶解性COD(SCOD)、溶解性蛋白质、溶解性糖类和VFA浓度均呈现先增加后降低的变化规律.水解0.5 d时,30 mg·g~(-1)(蛋白酶/TS)组和90 mg·g~(-1)(淀粉酶/TS)组的SCOD、溶解性蛋白质、溶解性糖类浓度均达到最大值.水解酸化4 d时,30 mg·g~(-1)(蛋白酶/TS)组和90 mg·g~(-1)(淀粉酶/TS)组的总VFA浓度分别为3373.39 mg·L~(-1)(以COD计,下同)和3226.79 mg·L~(-1),比预处理组分别提高了82.37%、74.45%.30 mg·g~(-1)(蛋白酶/TS)组和90 mg·g~(-1)(淀粉酶/TS)组的VFA主要组分均为乙酸、正丁酸和异戊酸,其中,乙酸占总VFA的比例分别为46.53%、45.94%,污泥上清液中的COD/总氮(TN)比分别为13.26、14.41.在碳源组成方面,在水解酸化0.5~4.0 d之内,30 mg·g~(-1)(蛋白酶/TS)组和90 mg·g~(-1)(淀粉酶/TS)组的SCOD浓度基本不变,但随着水解酸化时间的延长,溶解性蛋白质占SCOD的比例均在下降,总VFA占SCOD的比例均在提高,实现了在不改变碳源总量的条件下增加易生物降解有机物比例的目的.     

离子液体强化剩余污泥厌氧发酵产酸效能研究

针对污水处理厂剩余污泥厌氧发酵过程中有机质水解慢和酸化率低的问题,本文采用离子液体预处理促进污泥增溶破胞,并考察其对污泥厌氧发酵过程中有机质水解速率和短链脂肪酸(short-chain fatty acids, SCFAs)产量的影响.结果表明:投加离子液体[Emim]OTF能显著促进污泥溶胞,提高污泥水解速率及SCFAs产量,抑制污泥发酵产气;当离子液体投加量为0.1g/g VSS时,最大SCFAs产量可达226.4mg COD/(g TS),是未经预处理污泥的3.75倍;通过微生物多样性分析发现,投加离子液体[Emim]OTF富集了水解产酸菌,强化了污泥水解和酸化过程,从而导致SCFAs产量提高.     

胞外多聚物对酶催化污泥厌氧水解的影响研究

研究了胞外多聚物对酶催化污泥溶解效果和催化过程中污泥化学组分变化的影响.向原污泥及去除胞外多聚物的剩余污泥外加酶,并与未加酶组水解效果进行对比.结果表明,酶浓度〈20 mg/g时仅水解污泥胞外物质,加大酶量能显著引起污泥破解.溶菌酶用于原污泥水解效果较好,SCOD/TCOD最高可达28.14%,投加量60 mg/g,反...     

直链烷基苯磺酸盐促进剩余污泥产生短链脂肪酸的研究

采用批试试验的方法研究了十二烷基苯磺酸钠(C12-LAS)对剩余污泥在厌氧发酵过程中产生的短链脂肪酸(SCFAs)的影响.结果表明,C12-LAS的投加极大地提高了剩余污泥厌氧发酵过程中的SCFAs产量.当C12-LAS加入量低于0.1g·g-1时,SCFAs产量随着C12-LAS加入量的增加而增加,然而,当C12-LAS加入量高于0.1g·g-1时,SCFAs产量反而有所降低.从污泥产酸量以及经济成本考虑,C12-LAS的最佳投加量为0.02g·g-1,此时剩余污泥的SCFAs最大产量出现在第6天.进一步的研究表明,C12-LAS不仅促使大量的碳水化合物和蛋白质脱离污泥颗粒并溶解到液相中,而且抑制了产甲烷菌的活性.尽管剩余污泥经历着酸化过程,但由于其释放出大量的NH4 -N,污泥在整个厌氧发酵过程中的pH值逐渐升高.     

外加酶强化剩余污泥微生物燃料电池产电特性的研究

以剩余污泥作为接种液和基质,探讨了外加酶(中性蛋白酶、α-淀粉酶)强化单室型剩余污泥微生物燃料电池产电效率的可行性,研究了酶投加量对微生物燃料电池的产电特性及剩余污泥减量的影响.结果表明,在相同条件下,实验组产生的最大功率密度远远高于对照组;当酶的总投加量为10 mg.g-1时,最大输出功率密度及污泥水解效率达到最大,即中性蛋白酶组的最大功率密度、库仑效率、TCOD去除率、TSS去除率、VSS去除率分别为507 mW.m-2、3.98%、88.31%、83.18%、89.03%,而α-淀粉酶组则分别为700 mW.m-2、5.11%、94.09%、98.02%、98.80%.本实验采用向剩余污泥中投加酶的方法,成功增强了微生物燃料电池的产电效率,同时对剩余污泥有效地进行了处理,为微生物燃料电池的实际应用提供了新途径.     

亚硝酸盐对乳酸发酵缺氧-好氧SBR脱氮系统除磷的影响

在以可溶性淀粉为唯一碳源、进水含有硝态氮的缺氧-好氧SBR脱氮除磷系统中,研究了投配亚硝态氮对该乳酸发酵系统除磷的影响.试验结果显示,初始投加亚硝酸盐的浓度分别为2、5、10 mg·L~(-1)时对系统的缺氧吸磷及好氧吸磷都产生了抑制作用,缺氧阶段的释磷量和释磷速率随进水亚硝酸盐浓度的增大而升高.亚硝酸盐对缺氧期液相中乳酸和污泥中糖原的积累都有明显的影响,当亚硝酸盐浓度由0 mg·L~(-1)升至10 mg·L~(-1)时,乳酸浓度由14.06 mg·L~(-1)下降至1.56 mg·L~(-1),相反污泥中糖原的含量从235.69 mg·g~(-1)上升至272.97 mg·g~(-1)(以VSS计,下同),并且在好氧阶段糖原的消耗量增加,污泥的吸磷量也随之增加.研究表明,亚硝酸盐对淀粉直接发酵成乳酸的过程及糖原转化为乳酸的过程均有抑制作用.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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